linux-kernel - Re: [PATCH] x86: Add an explicit barrier() to clflushopt()

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Message-ID: <568ED31F.1090004@zytor.com>
Date:	Thu, 7 Jan 2016 13:05:35 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Chris Wilson <chris@...is-wilson.co.uk>,
	Andy Lutomirski <luto@...capital.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ross Zwisler <ross.zwisler@...ux.intel.com>,
	"H . Peter Anvin" <hpa@...ux.intel.com>,
	Borislav Petkov <bp@...en8.de>,
	Brian Gerst <brgerst@...il.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Imre Deak <imre.deak@...el.com>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	DRI <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH] x86: Add an explicit barrier() to clflushopt()

On 01/07/16 11:44, Chris Wilson wrote:
> 
> Now I feel silly. Looking at the .s, there is no difference with the
> addition of the barrier to clflush_cache_range(). And sure enough
> letting the test run for longer, we see a failure. I fell for a placebo.
> 
> The failing assertion is always on the last cacheline and is always one
> value behind. Oh well, back to wondering where we miss the flush.
> -Chris
> 

Could you include the assembly here?

	-hpa